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-rw-r--r--tools/lib/bpf/btf_dump.c1531
1 files changed, 1531 insertions, 0 deletions
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
new file mode 100644
index 000000000..61aa2c47f
--- /dev/null
+++ b/tools/lib/bpf/btf_dump.c
@@ -0,0 +1,1531 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+
+/*
+ * BTF-to-C type converter.
+ *
+ * Copyright (c) 2019 Facebook
+ */
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <linux/err.h>
+#include <linux/btf.h>
+#include <linux/kernel.h>
+#include "btf.h"
+#include "hashmap.h"
+#include "libbpf.h"
+#include "libbpf_internal.h"
+
+static const char PREFIXES[] = "\t\t\t\t\t\t\t\t\t\t\t\t\t";
+static const size_t PREFIX_CNT = sizeof(PREFIXES) - 1;
+
+static const char *pfx(int lvl)
+{
+ return lvl >= PREFIX_CNT ? PREFIXES : &PREFIXES[PREFIX_CNT - lvl];
+}
+
+enum btf_dump_type_order_state {
+ NOT_ORDERED,
+ ORDERING,
+ ORDERED,
+};
+
+enum btf_dump_type_emit_state {
+ NOT_EMITTED,
+ EMITTING,
+ EMITTED,
+};
+
+/* per-type auxiliary state */
+struct btf_dump_type_aux_state {
+ /* topological sorting state */
+ enum btf_dump_type_order_state order_state: 2;
+ /* emitting state used to determine the need for forward declaration */
+ enum btf_dump_type_emit_state emit_state: 2;
+ /* whether forward declaration was already emitted */
+ __u8 fwd_emitted: 1;
+ /* whether unique non-duplicate name was already assigned */
+ __u8 name_resolved: 1;
+ /* whether type is referenced from any other type */
+ __u8 referenced: 1;
+};
+
+struct btf_dump {
+ const struct btf *btf;
+ const struct btf_ext *btf_ext;
+ btf_dump_printf_fn_t printf_fn;
+ struct btf_dump_opts opts;
+ int ptr_sz;
+ bool strip_mods;
+ int last_id;
+
+ /* per-type auxiliary state */
+ struct btf_dump_type_aux_state *type_states;
+ size_t type_states_cap;
+ /* per-type optional cached unique name, must be freed, if present */
+ const char **cached_names;
+ size_t cached_names_cap;
+
+ /* topo-sorted list of dependent type definitions */
+ __u32 *emit_queue;
+ int emit_queue_cap;
+ int emit_queue_cnt;
+
+ /*
+ * stack of type declarations (e.g., chain of modifiers, arrays,
+ * funcs, etc)
+ */
+ __u32 *decl_stack;
+ int decl_stack_cap;
+ int decl_stack_cnt;
+
+ /* maps struct/union/enum name to a number of name occurrences */
+ struct hashmap *type_names;
+ /*
+ * maps typedef identifiers and enum value names to a number of such
+ * name occurrences
+ */
+ struct hashmap *ident_names;
+};
+
+static size_t str_hash_fn(const void *key, void *ctx)
+{
+ return str_hash(key);
+}
+
+static bool str_equal_fn(const void *a, const void *b, void *ctx)
+{
+ return strcmp(a, b) == 0;
+}
+
+static const char *btf_name_of(const struct btf_dump *d, __u32 name_off)
+{
+ return btf__name_by_offset(d->btf, name_off);
+}
+
+static void btf_dump_printf(const struct btf_dump *d, const char *fmt, ...)
+{
+ va_list args;
+
+ va_start(args, fmt);
+ d->printf_fn(d->opts.ctx, fmt, args);
+ va_end(args);
+}
+
+static int btf_dump_mark_referenced(struct btf_dump *d);
+static int btf_dump_resize(struct btf_dump *d);
+
+struct btf_dump *btf_dump__new(const struct btf *btf,
+ const struct btf_ext *btf_ext,
+ const struct btf_dump_opts *opts,
+ btf_dump_printf_fn_t printf_fn)
+{
+ struct btf_dump *d;
+ int err;
+
+ d = calloc(1, sizeof(struct btf_dump));
+ if (!d)
+ return ERR_PTR(-ENOMEM);
+
+ d->btf = btf;
+ d->btf_ext = btf_ext;
+ d->printf_fn = printf_fn;
+ d->opts.ctx = opts ? opts->ctx : NULL;
+ d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *);
+
+ d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
+ if (IS_ERR(d->type_names)) {
+ err = PTR_ERR(d->type_names);
+ d->type_names = NULL;
+ goto err;
+ }
+ d->ident_names = hashmap__new(str_hash_fn, str_equal_fn, NULL);
+ if (IS_ERR(d->ident_names)) {
+ err = PTR_ERR(d->ident_names);
+ d->ident_names = NULL;
+ goto err;
+ }
+
+ err = btf_dump_resize(d);
+ if (err)
+ goto err;
+
+ return d;
+err:
+ btf_dump__free(d);
+ return ERR_PTR(err);
+}
+
+static int btf_dump_resize(struct btf_dump *d)
+{
+ int err, last_id = btf__get_nr_types(d->btf);
+
+ if (last_id <= d->last_id)
+ return 0;
+
+ if (btf_ensure_mem((void **)&d->type_states, &d->type_states_cap,
+ sizeof(*d->type_states), last_id + 1))
+ return -ENOMEM;
+ if (btf_ensure_mem((void **)&d->cached_names, &d->cached_names_cap,
+ sizeof(*d->cached_names), last_id + 1))
+ return -ENOMEM;
+
+ if (d->last_id == 0) {
+ /* VOID is special */
+ d->type_states[0].order_state = ORDERED;
+ d->type_states[0].emit_state = EMITTED;
+ }
+
+ /* eagerly determine referenced types for anon enums */
+ err = btf_dump_mark_referenced(d);
+ if (err)
+ return err;
+
+ d->last_id = last_id;
+ return 0;
+}
+
+static void btf_dump_free_names(struct hashmap *map)
+{
+ size_t bkt;
+ struct hashmap_entry *cur;
+
+ hashmap__for_each_entry(map, cur, bkt)
+ free((void *)cur->key);
+
+ hashmap__free(map);
+}
+
+void btf_dump__free(struct btf_dump *d)
+{
+ int i;
+
+ if (IS_ERR_OR_NULL(d))
+ return;
+
+ free(d->type_states);
+ if (d->cached_names) {
+ /* any set cached name is owned by us and should be freed */
+ for (i = 0; i <= d->last_id; i++) {
+ if (d->cached_names[i])
+ free((void *)d->cached_names[i]);
+ }
+ }
+ free(d->cached_names);
+ free(d->emit_queue);
+ free(d->decl_stack);
+ btf_dump_free_names(d->type_names);
+ btf_dump_free_names(d->ident_names);
+
+ free(d);
+}
+
+static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr);
+static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id);
+
+/*
+ * Dump BTF type in a compilable C syntax, including all the necessary
+ * dependent types, necessary for compilation. If some of the dependent types
+ * were already emitted as part of previous btf_dump__dump_type() invocation
+ * for another type, they won't be emitted again. This API allows callers to
+ * filter out BTF types according to user-defined criterias and emitted only
+ * minimal subset of types, necessary to compile everything. Full struct/union
+ * definitions will still be emitted, even if the only usage is through
+ * pointer and could be satisfied with just a forward declaration.
+ *
+ * Dumping is done in two high-level passes:
+ * 1. Topologically sort type definitions to satisfy C rules of compilation.
+ * 2. Emit type definitions in C syntax.
+ *
+ * Returns 0 on success; <0, otherwise.
+ */
+int btf_dump__dump_type(struct btf_dump *d, __u32 id)
+{
+ int err, i;
+
+ if (id > btf__get_nr_types(d->btf))
+ return -EINVAL;
+
+ err = btf_dump_resize(d);
+ if (err)
+ return err;
+
+ d->emit_queue_cnt = 0;
+ err = btf_dump_order_type(d, id, false);
+ if (err < 0)
+ return err;
+
+ for (i = 0; i < d->emit_queue_cnt; i++)
+ btf_dump_emit_type(d, d->emit_queue[i], 0 /*top-level*/);
+
+ return 0;
+}
+
+/*
+ * Mark all types that are referenced from any other type. This is used to
+ * determine top-level anonymous enums that need to be emitted as an
+ * independent type declarations.
+ * Anonymous enums come in two flavors: either embedded in a struct's field
+ * definition, in which case they have to be declared inline as part of field
+ * type declaration; or as a top-level anonymous enum, typically used for
+ * declaring global constants. It's impossible to distinguish between two
+ * without knowning whether given enum type was referenced from other type:
+ * top-level anonymous enum won't be referenced by anything, while embedded
+ * one will.
+ */
+static int btf_dump_mark_referenced(struct btf_dump *d)
+{
+ int i, j, n = btf__get_nr_types(d->btf);
+ const struct btf_type *t;
+ __u16 vlen;
+
+ for (i = d->last_id + 1; i <= n; i++) {
+ t = btf__type_by_id(d->btf, i);
+ vlen = btf_vlen(t);
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_INT:
+ case BTF_KIND_ENUM:
+ case BTF_KIND_FWD:
+ break;
+
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ case BTF_KIND_PTR:
+ case BTF_KIND_TYPEDEF:
+ case BTF_KIND_FUNC:
+ case BTF_KIND_VAR:
+ d->type_states[t->type].referenced = 1;
+ break;
+
+ case BTF_KIND_ARRAY: {
+ const struct btf_array *a = btf_array(t);
+
+ d->type_states[a->index_type].referenced = 1;
+ d->type_states[a->type].referenced = 1;
+ break;
+ }
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION: {
+ const struct btf_member *m = btf_members(t);
+
+ for (j = 0; j < vlen; j++, m++)
+ d->type_states[m->type].referenced = 1;
+ break;
+ }
+ case BTF_KIND_FUNC_PROTO: {
+ const struct btf_param *p = btf_params(t);
+
+ for (j = 0; j < vlen; j++, p++)
+ d->type_states[p->type].referenced = 1;
+ break;
+ }
+ case BTF_KIND_DATASEC: {
+ const struct btf_var_secinfo *v = btf_var_secinfos(t);
+
+ for (j = 0; j < vlen; j++, v++)
+ d->type_states[v->type].referenced = 1;
+ break;
+ }
+ default:
+ return -EINVAL;
+ }
+ }
+ return 0;
+}
+
+static int btf_dump_add_emit_queue_id(struct btf_dump *d, __u32 id)
+{
+ __u32 *new_queue;
+ size_t new_cap;
+
+ if (d->emit_queue_cnt >= d->emit_queue_cap) {
+ new_cap = max(16, d->emit_queue_cap * 3 / 2);
+ new_queue = libbpf_reallocarray(d->emit_queue, new_cap, sizeof(new_queue[0]));
+ if (!new_queue)
+ return -ENOMEM;
+ d->emit_queue = new_queue;
+ d->emit_queue_cap = new_cap;
+ }
+
+ d->emit_queue[d->emit_queue_cnt++] = id;
+ return 0;
+}
+
+/*
+ * Determine order of emitting dependent types and specified type to satisfy
+ * C compilation rules. This is done through topological sorting with an
+ * additional complication which comes from C rules. The main idea for C is
+ * that if some type is "embedded" into a struct/union, it's size needs to be
+ * known at the time of definition of containing type. E.g., for:
+ *
+ * struct A {};
+ * struct B { struct A x; }
+ *
+ * struct A *HAS* to be defined before struct B, because it's "embedded",
+ * i.e., it is part of struct B layout. But in the following case:
+ *
+ * struct A;
+ * struct B { struct A *x; }
+ * struct A {};
+ *
+ * it's enough to just have a forward declaration of struct A at the time of
+ * struct B definition, as struct B has a pointer to struct A, so the size of
+ * field x is known without knowing struct A size: it's sizeof(void *).
+ *
+ * Unfortunately, there are some trickier cases we need to handle, e.g.:
+ *
+ * struct A {}; // if this was forward-declaration: compilation error
+ * struct B {
+ * struct { // anonymous struct
+ * struct A y;
+ * } *x;
+ * };
+ *
+ * In this case, struct B's field x is a pointer, so it's size is known
+ * regardless of the size of (anonymous) struct it points to. But because this
+ * struct is anonymous and thus defined inline inside struct B, *and* it
+ * embeds struct A, compiler requires full definition of struct A to be known
+ * before struct B can be defined. This creates a transitive dependency
+ * between struct A and struct B. If struct A was forward-declared before
+ * struct B definition and fully defined after struct B definition, that would
+ * trigger compilation error.
+ *
+ * All this means that while we are doing topological sorting on BTF type
+ * graph, we need to determine relationships between different types (graph
+ * nodes):
+ * - weak link (relationship) between X and Y, if Y *CAN* be
+ * forward-declared at the point of X definition;
+ * - strong link, if Y *HAS* to be fully-defined before X can be defined.
+ *
+ * The rule is as follows. Given a chain of BTF types from X to Y, if there is
+ * BTF_KIND_PTR type in the chain and at least one non-anonymous type
+ * Z (excluding X, including Y), then link is weak. Otherwise, it's strong.
+ * Weak/strong relationship is determined recursively during DFS traversal and
+ * is returned as a result from btf_dump_order_type().
+ *
+ * btf_dump_order_type() is trying to avoid unnecessary forward declarations,
+ * but it is not guaranteeing that no extraneous forward declarations will be
+ * emitted.
+ *
+ * To avoid extra work, algorithm marks some of BTF types as ORDERED, when
+ * it's done with them, but not for all (e.g., VOLATILE, CONST, RESTRICT,
+ * ARRAY, FUNC_PROTO), as weak/strong semantics for those depends on the
+ * entire graph path, so depending where from one came to that BTF type, it
+ * might cause weak or strong ordering. For types like STRUCT/UNION/INT/ENUM,
+ * once they are processed, there is no need to do it again, so they are
+ * marked as ORDERED. We can mark PTR as ORDERED as well, as it semi-forces
+ * weak link, unless subsequent referenced STRUCT/UNION/ENUM is anonymous. But
+ * in any case, once those are processed, no need to do it again, as the
+ * result won't change.
+ *
+ * Returns:
+ * - 1, if type is part of strong link (so there is strong topological
+ * ordering requirements);
+ * - 0, if type is part of weak link (so can be satisfied through forward
+ * declaration);
+ * - <0, on error (e.g., unsatisfiable type loop detected).
+ */
+static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr)
+{
+ /*
+ * Order state is used to detect strong link cycles, but only for BTF
+ * kinds that are or could be an independent definition (i.e.,
+ * stand-alone fwd decl, enum, typedef, struct, union). Ptrs, arrays,
+ * func_protos, modifiers are just means to get to these definitions.
+ * Int/void don't need definitions, they are assumed to be always
+ * properly defined. We also ignore datasec, var, and funcs for now.
+ * So for all non-defining kinds, we never even set ordering state,
+ * for defining kinds we set ORDERING and subsequently ORDERED if it
+ * forms a strong link.
+ */
+ struct btf_dump_type_aux_state *tstate = &d->type_states[id];
+ const struct btf_type *t;
+ __u16 vlen;
+ int err, i;
+
+ /* return true, letting typedefs know that it's ok to be emitted */
+ if (tstate->order_state == ORDERED)
+ return 1;
+
+ t = btf__type_by_id(d->btf, id);
+
+ if (tstate->order_state == ORDERING) {
+ /* type loop, but resolvable through fwd declaration */
+ if (btf_is_composite(t) && through_ptr && t->name_off != 0)
+ return 0;
+ pr_warn("unsatisfiable type cycle, id:[%u]\n", id);
+ return -ELOOP;
+ }
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_INT:
+ tstate->order_state = ORDERED;
+ return 0;
+
+ case BTF_KIND_PTR:
+ err = btf_dump_order_type(d, t->type, true);
+ tstate->order_state = ORDERED;
+ return err;
+
+ case BTF_KIND_ARRAY:
+ return btf_dump_order_type(d, btf_array(t)->type, false);
+
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION: {
+ const struct btf_member *m = btf_members(t);
+ /*
+ * struct/union is part of strong link, only if it's embedded
+ * (so no ptr in a path) or it's anonymous (so has to be
+ * defined inline, even if declared through ptr)
+ */
+ if (through_ptr && t->name_off != 0)
+ return 0;
+
+ tstate->order_state = ORDERING;
+
+ vlen = btf_vlen(t);
+ for (i = 0; i < vlen; i++, m++) {
+ err = btf_dump_order_type(d, m->type, false);
+ if (err < 0)
+ return err;
+ }
+
+ if (t->name_off != 0) {
+ err = btf_dump_add_emit_queue_id(d, id);
+ if (err < 0)
+ return err;
+ }
+
+ tstate->order_state = ORDERED;
+ return 1;
+ }
+ case BTF_KIND_ENUM:
+ case BTF_KIND_FWD:
+ /*
+ * non-anonymous or non-referenced enums are top-level
+ * declarations and should be emitted. Same logic can be
+ * applied to FWDs, it won't hurt anyways.
+ */
+ if (t->name_off != 0 || !tstate->referenced) {
+ err = btf_dump_add_emit_queue_id(d, id);
+ if (err)
+ return err;
+ }
+ tstate->order_state = ORDERED;
+ return 1;
+
+ case BTF_KIND_TYPEDEF: {
+ int is_strong;
+
+ is_strong = btf_dump_order_type(d, t->type, through_ptr);
+ if (is_strong < 0)
+ return is_strong;
+
+ /* typedef is similar to struct/union w.r.t. fwd-decls */
+ if (through_ptr && !is_strong)
+ return 0;
+
+ /* typedef is always a named definition */
+ err = btf_dump_add_emit_queue_id(d, id);
+ if (err)
+ return err;
+
+ d->type_states[id].order_state = ORDERED;
+ return 1;
+ }
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ return btf_dump_order_type(d, t->type, through_ptr);
+
+ case BTF_KIND_FUNC_PROTO: {
+ const struct btf_param *p = btf_params(t);
+ bool is_strong;
+
+ err = btf_dump_order_type(d, t->type, through_ptr);
+ if (err < 0)
+ return err;
+ is_strong = err > 0;
+
+ vlen = btf_vlen(t);
+ for (i = 0; i < vlen; i++, p++) {
+ err = btf_dump_order_type(d, p->type, through_ptr);
+ if (err < 0)
+ return err;
+ if (err > 0)
+ is_strong = true;
+ }
+ return is_strong;
+ }
+ case BTF_KIND_FUNC:
+ case BTF_KIND_VAR:
+ case BTF_KIND_DATASEC:
+ d->type_states[id].order_state = ORDERED;
+ return 0;
+
+ default:
+ return -EINVAL;
+ }
+}
+
+static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
+ const struct btf_type *t);
+
+static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
+ const struct btf_type *t);
+static void btf_dump_emit_struct_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t, int lvl);
+
+static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
+ const struct btf_type *t);
+static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t, int lvl);
+
+static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t);
+
+static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t, int lvl);
+
+/* a local view into a shared stack */
+struct id_stack {
+ const __u32 *ids;
+ int cnt;
+};
+
+static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
+ const char *fname, int lvl);
+static void btf_dump_emit_type_chain(struct btf_dump *d,
+ struct id_stack *decl_stack,
+ const char *fname, int lvl);
+
+static const char *btf_dump_type_name(struct btf_dump *d, __u32 id);
+static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id);
+static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
+ const char *orig_name);
+
+static bool btf_dump_is_blacklisted(struct btf_dump *d, __u32 id)
+{
+ const struct btf_type *t = btf__type_by_id(d->btf, id);
+
+ /* __builtin_va_list is a compiler built-in, which causes compilation
+ * errors, when compiling w/ different compiler, then used to compile
+ * original code (e.g., GCC to compile kernel, Clang to use generated
+ * C header from BTF). As it is built-in, it should be already defined
+ * properly internally in compiler.
+ */
+ if (t->name_off == 0)
+ return false;
+ return strcmp(btf_name_of(d, t->name_off), "__builtin_va_list") == 0;
+}
+
+/*
+ * Emit C-syntax definitions of types from chains of BTF types.
+ *
+ * High-level handling of determining necessary forward declarations are handled
+ * by btf_dump_emit_type() itself, but all nitty-gritty details of emitting type
+ * declarations/definitions in C syntax are handled by a combo of
+ * btf_dump_emit_type_decl()/btf_dump_emit_type_chain() w/ delegation to
+ * corresponding btf_dump_emit_*_{def,fwd}() functions.
+ *
+ * We also keep track of "containing struct/union type ID" to determine when
+ * we reference it from inside and thus can avoid emitting unnecessary forward
+ * declaration.
+ *
+ * This algorithm is designed in such a way, that even if some error occurs
+ * (either technical, e.g., out of memory, or logical, i.e., malformed BTF
+ * that doesn't comply to C rules completely), algorithm will try to proceed
+ * and produce as much meaningful output as possible.
+ */
+static void btf_dump_emit_type(struct btf_dump *d, __u32 id, __u32 cont_id)
+{
+ struct btf_dump_type_aux_state *tstate = &d->type_states[id];
+ bool top_level_def = cont_id == 0;
+ const struct btf_type *t;
+ __u16 kind;
+
+ if (tstate->emit_state == EMITTED)
+ return;
+
+ t = btf__type_by_id(d->btf, id);
+ kind = btf_kind(t);
+
+ if (tstate->emit_state == EMITTING) {
+ if (tstate->fwd_emitted)
+ return;
+
+ switch (kind) {
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ /*
+ * if we are referencing a struct/union that we are
+ * part of - then no need for fwd declaration
+ */
+ if (id == cont_id)
+ return;
+ if (t->name_off == 0) {
+ pr_warn("anonymous struct/union loop, id:[%u]\n",
+ id);
+ return;
+ }
+ btf_dump_emit_struct_fwd(d, id, t);
+ btf_dump_printf(d, ";\n\n");
+ tstate->fwd_emitted = 1;
+ break;
+ case BTF_KIND_TYPEDEF:
+ /*
+ * for typedef fwd_emitted means typedef definition
+ * was emitted, but it can be used only for "weak"
+ * references through pointer only, not for embedding
+ */
+ if (!btf_dump_is_blacklisted(d, id)) {
+ btf_dump_emit_typedef_def(d, id, t, 0);
+ btf_dump_printf(d, ";\n\n");
+ }
+ tstate->fwd_emitted = 1;
+ break;
+ default:
+ break;
+ }
+
+ return;
+ }
+
+ switch (kind) {
+ case BTF_KIND_INT:
+ /* Emit type alias definitions if necessary */
+ btf_dump_emit_missing_aliases(d, id, t);
+
+ tstate->emit_state = EMITTED;
+ break;
+ case BTF_KIND_ENUM:
+ if (top_level_def) {
+ btf_dump_emit_enum_def(d, id, t, 0);
+ btf_dump_printf(d, ";\n\n");
+ }
+ tstate->emit_state = EMITTED;
+ break;
+ case BTF_KIND_PTR:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ btf_dump_emit_type(d, t->type, cont_id);
+ break;
+ case BTF_KIND_ARRAY:
+ btf_dump_emit_type(d, btf_array(t)->type, cont_id);
+ break;
+ case BTF_KIND_FWD:
+ btf_dump_emit_fwd_def(d, id, t);
+ btf_dump_printf(d, ";\n\n");
+ tstate->emit_state = EMITTED;
+ break;
+ case BTF_KIND_TYPEDEF:
+ tstate->emit_state = EMITTING;
+ btf_dump_emit_type(d, t->type, id);
+ /*
+ * typedef can server as both definition and forward
+ * declaration; at this stage someone depends on
+ * typedef as a forward declaration (refers to it
+ * through pointer), so unless we already did it,
+ * emit typedef as a forward declaration
+ */
+ if (!tstate->fwd_emitted && !btf_dump_is_blacklisted(d, id)) {
+ btf_dump_emit_typedef_def(d, id, t, 0);
+ btf_dump_printf(d, ";\n\n");
+ }
+ tstate->emit_state = EMITTED;
+ break;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ tstate->emit_state = EMITTING;
+ /* if it's a top-level struct/union definition or struct/union
+ * is anonymous, then in C we'll be emitting all fields and
+ * their types (as opposed to just `struct X`), so we need to
+ * make sure that all types, referenced from struct/union
+ * members have necessary forward-declarations, where
+ * applicable
+ */
+ if (top_level_def || t->name_off == 0) {
+ const struct btf_member *m = btf_members(t);
+ __u16 vlen = btf_vlen(t);
+ int i, new_cont_id;
+
+ new_cont_id = t->name_off == 0 ? cont_id : id;
+ for (i = 0; i < vlen; i++, m++)
+ btf_dump_emit_type(d, m->type, new_cont_id);
+ } else if (!tstate->fwd_emitted && id != cont_id) {
+ btf_dump_emit_struct_fwd(d, id, t);
+ btf_dump_printf(d, ";\n\n");
+ tstate->fwd_emitted = 1;
+ }
+
+ if (top_level_def) {
+ btf_dump_emit_struct_def(d, id, t, 0);
+ btf_dump_printf(d, ";\n\n");
+ tstate->emit_state = EMITTED;
+ } else {
+ tstate->emit_state = NOT_EMITTED;
+ }
+ break;
+ case BTF_KIND_FUNC_PROTO: {
+ const struct btf_param *p = btf_params(t);
+ __u16 vlen = btf_vlen(t);
+ int i;
+
+ btf_dump_emit_type(d, t->type, cont_id);
+ for (i = 0; i < vlen; i++, p++)
+ btf_dump_emit_type(d, p->type, cont_id);
+
+ break;
+ }
+ default:
+ break;
+ }
+}
+
+static bool btf_is_struct_packed(const struct btf *btf, __u32 id,
+ const struct btf_type *t)
+{
+ const struct btf_member *m;
+ int max_align = 1, align, i, bit_sz;
+ __u16 vlen;
+
+ m = btf_members(t);
+ vlen = btf_vlen(t);
+ /* all non-bitfield fields have to be naturally aligned */
+ for (i = 0; i < vlen; i++, m++) {
+ align = btf__align_of(btf, m->type);
+ bit_sz = btf_member_bitfield_size(t, i);
+ if (align && bit_sz == 0 && m->offset % (8 * align) != 0)
+ return true;
+ max_align = max(align, max_align);
+ }
+ /* size of a non-packed struct has to be a multiple of its alignment */
+ if (t->size % max_align != 0)
+ return true;
+ /*
+ * if original struct was marked as packed, but its layout is
+ * naturally aligned, we'll detect that it's not packed
+ */
+ return false;
+}
+
+static void btf_dump_emit_bit_padding(const struct btf_dump *d,
+ int cur_off, int next_off, int next_align,
+ bool in_bitfield, int lvl)
+{
+ const struct {
+ const char *name;
+ int bits;
+ } pads[] = {
+ {"long", d->ptr_sz * 8}, {"int", 32}, {"short", 16}, {"char", 8}
+ };
+ int new_off, pad_bits, bits, i;
+ const char *pad_type;
+
+ if (cur_off >= next_off)
+ return; /* no gap */
+
+ /* For filling out padding we want to take advantage of
+ * natural alignment rules to minimize unnecessary explicit
+ * padding. First, we find the largest type (among long, int,
+ * short, or char) that can be used to force naturally aligned
+ * boundary. Once determined, we'll use such type to fill in
+ * the remaining padding gap. In some cases we can rely on
+ * compiler filling some gaps, but sometimes we need to force
+ * alignment to close natural alignment with markers like
+ * `long: 0` (this is always the case for bitfields). Note
+ * that even if struct itself has, let's say 4-byte alignment
+ * (i.e., it only uses up to int-aligned types), using `long:
+ * X;` explicit padding doesn't actually change struct's
+ * overall alignment requirements, but compiler does take into
+ * account that type's (long, in this example) natural
+ * alignment requirements when adding implicit padding. We use
+ * this fact heavily and don't worry about ruining correct
+ * struct alignment requirement.
+ */
+ for (i = 0; i < ARRAY_SIZE(pads); i++) {
+ pad_bits = pads[i].bits;
+ pad_type = pads[i].name;
+
+ new_off = roundup(cur_off, pad_bits);
+ if (new_off <= next_off)
+ break;
+ }
+
+ if (new_off > cur_off && new_off <= next_off) {
+ /* We need explicit `<type>: 0` aligning mark if next
+ * field is right on alignment offset and its
+ * alignment requirement is less strict than <type>'s
+ * alignment (so compiler won't naturally align to the
+ * offset we expect), or if subsequent `<type>: X`,
+ * will actually completely fit in the remaining hole,
+ * making compiler basically ignore `<type>: X`
+ * completely.
+ */
+ if (in_bitfield ||
+ (new_off == next_off && roundup(cur_off, next_align * 8) != new_off) ||
+ (new_off != next_off && next_off - new_off <= new_off - cur_off))
+ /* but for bitfields we'll emit explicit bit count */
+ btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type,
+ in_bitfield ? new_off - cur_off : 0);
+ cur_off = new_off;
+ }
+
+ /* Now we know we start at naturally aligned offset for a chosen
+ * padding type (long, int, short, or char), and so the rest is just
+ * a straightforward filling of remaining padding gap with full
+ * `<type>: sizeof(<type>);` markers, except for the last one, which
+ * might need smaller than sizeof(<type>) padding.
+ */
+ while (cur_off != next_off) {
+ bits = min(next_off - cur_off, pad_bits);
+ if (bits == pad_bits) {
+ btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, pad_bits);
+ cur_off += bits;
+ continue;
+ }
+ /* For the remainder padding that doesn't cover entire
+ * pad_type bit length, we pick the smallest necessary type.
+ * This is pure aesthetics, we could have just used `long`,
+ * but having smallest necessary one communicates better the
+ * scale of the padding gap.
+ */
+ for (i = ARRAY_SIZE(pads) - 1; i >= 0; i--) {
+ pad_type = pads[i].name;
+ pad_bits = pads[i].bits;
+ if (pad_bits < bits)
+ continue;
+
+ btf_dump_printf(d, "\n%s%s: %d;", pfx(lvl), pad_type, bits);
+ cur_off += bits;
+ break;
+ }
+ }
+}
+
+static void btf_dump_emit_struct_fwd(struct btf_dump *d, __u32 id,
+ const struct btf_type *t)
+{
+ btf_dump_printf(d, "%s %s",
+ btf_is_struct(t) ? "struct" : "union",
+ btf_dump_type_name(d, id));
+}
+
+static void btf_dump_emit_struct_def(struct btf_dump *d,
+ __u32 id,
+ const struct btf_type *t,
+ int lvl)
+{
+ const struct btf_member *m = btf_members(t);
+ bool is_struct = btf_is_struct(t);
+ bool packed, prev_bitfield = false;
+ int align, i, off = 0;
+ __u16 vlen = btf_vlen(t);
+
+ align = btf__align_of(d->btf, id);
+ packed = is_struct ? btf_is_struct_packed(d->btf, id, t) : 0;
+
+ btf_dump_printf(d, "%s%s%s {",
+ is_struct ? "struct" : "union",
+ t->name_off ? " " : "",
+ btf_dump_type_name(d, id));
+
+ for (i = 0; i < vlen; i++, m++) {
+ const char *fname;
+ int m_off, m_sz, m_align;
+ bool in_bitfield;
+
+ fname = btf_name_of(d, m->name_off);
+ m_sz = btf_member_bitfield_size(t, i);
+ m_off = btf_member_bit_offset(t, i);
+ m_align = packed ? 1 : btf__align_of(d->btf, m->type);
+
+ in_bitfield = prev_bitfield && m_sz != 0;
+
+ btf_dump_emit_bit_padding(d, off, m_off, m_align, in_bitfield, lvl + 1);
+ btf_dump_printf(d, "\n%s", pfx(lvl + 1));
+ btf_dump_emit_type_decl(d, m->type, fname, lvl + 1);
+
+ if (m_sz) {
+ btf_dump_printf(d, ": %d", m_sz);
+ off = m_off + m_sz;
+ prev_bitfield = true;
+ } else {
+ m_sz = max((__s64)0, btf__resolve_size(d->btf, m->type));
+ off = m_off + m_sz * 8;
+ prev_bitfield = false;
+ }
+
+ btf_dump_printf(d, ";");
+ }
+
+ /* pad at the end, if necessary */
+ if (is_struct)
+ btf_dump_emit_bit_padding(d, off, t->size * 8, align, false, lvl + 1);
+
+ /*
+ * Keep `struct empty {}` on a single line,
+ * only print newline when there are regular or padding fields.
+ */
+ if (vlen || t->size) {
+ btf_dump_printf(d, "\n");
+ btf_dump_printf(d, "%s}", pfx(lvl));
+ } else {
+ btf_dump_printf(d, "}");
+ }
+ if (packed)
+ btf_dump_printf(d, " __attribute__((packed))");
+}
+
+static const char *missing_base_types[][2] = {
+ /*
+ * GCC emits typedefs to its internal __PolyX_t types when compiling Arm
+ * SIMD intrinsics. Alias them to standard base types.
+ */
+ { "__Poly8_t", "unsigned char" },
+ { "__Poly16_t", "unsigned short" },
+ { "__Poly64_t", "unsigned long long" },
+ { "__Poly128_t", "unsigned __int128" },
+};
+
+static void btf_dump_emit_missing_aliases(struct btf_dump *d, __u32 id,
+ const struct btf_type *t)
+{
+ const char *name = btf_dump_type_name(d, id);
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(missing_base_types); i++) {
+ if (strcmp(name, missing_base_types[i][0]) == 0) {
+ btf_dump_printf(d, "typedef %s %s;\n\n",
+ missing_base_types[i][1], name);
+ break;
+ }
+ }
+}
+
+static void btf_dump_emit_enum_fwd(struct btf_dump *d, __u32 id,
+ const struct btf_type *t)
+{
+ btf_dump_printf(d, "enum %s", btf_dump_type_name(d, id));
+}
+
+static void btf_dump_emit_enum_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t,
+ int lvl)
+{
+ const struct btf_enum *v = btf_enum(t);
+ __u16 vlen = btf_vlen(t);
+ const char *name;
+ size_t dup_cnt;
+ int i;
+
+ btf_dump_printf(d, "enum%s%s",
+ t->name_off ? " " : "",
+ btf_dump_type_name(d, id));
+
+ if (vlen) {
+ btf_dump_printf(d, " {");
+ for (i = 0; i < vlen; i++, v++) {
+ name = btf_name_of(d, v->name_off);
+ /* enumerators share namespace with typedef idents */
+ dup_cnt = btf_dump_name_dups(d, d->ident_names, name);
+ if (dup_cnt > 1) {
+ btf_dump_printf(d, "\n%s%s___%zu = %u,",
+ pfx(lvl + 1), name, dup_cnt,
+ (__u32)v->val);
+ } else {
+ btf_dump_printf(d, "\n%s%s = %u,",
+ pfx(lvl + 1), name,
+ (__u32)v->val);
+ }
+ }
+ btf_dump_printf(d, "\n%s}", pfx(lvl));
+ }
+}
+
+static void btf_dump_emit_fwd_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t)
+{
+ const char *name = btf_dump_type_name(d, id);
+
+ if (btf_kflag(t))
+ btf_dump_printf(d, "union %s", name);
+ else
+ btf_dump_printf(d, "struct %s", name);
+}
+
+static void btf_dump_emit_typedef_def(struct btf_dump *d, __u32 id,
+ const struct btf_type *t, int lvl)
+{
+ const char *name = btf_dump_ident_name(d, id);
+
+ /*
+ * Old GCC versions are emitting invalid typedef for __gnuc_va_list
+ * pointing to VOID. This generates warnings from btf_dump() and
+ * results in uncompilable header file, so we are fixing it up here
+ * with valid typedef into __builtin_va_list.
+ */
+ if (t->type == 0 && strcmp(name, "__gnuc_va_list") == 0) {
+ btf_dump_printf(d, "typedef __builtin_va_list __gnuc_va_list");
+ return;
+ }
+
+ btf_dump_printf(d, "typedef ");
+ btf_dump_emit_type_decl(d, t->type, name, lvl);
+}
+
+static int btf_dump_push_decl_stack_id(struct btf_dump *d, __u32 id)
+{
+ __u32 *new_stack;
+ size_t new_cap;
+
+ if (d->decl_stack_cnt >= d->decl_stack_cap) {
+ new_cap = max(16, d->decl_stack_cap * 3 / 2);
+ new_stack = libbpf_reallocarray(d->decl_stack, new_cap, sizeof(new_stack[0]));
+ if (!new_stack)
+ return -ENOMEM;
+ d->decl_stack = new_stack;
+ d->decl_stack_cap = new_cap;
+ }
+
+ d->decl_stack[d->decl_stack_cnt++] = id;
+
+ return 0;
+}
+
+/*
+ * Emit type declaration (e.g., field type declaration in a struct or argument
+ * declaration in function prototype) in correct C syntax.
+ *
+ * For most types it's trivial, but there are few quirky type declaration
+ * cases worth mentioning:
+ * - function prototypes (especially nesting of function prototypes);
+ * - arrays;
+ * - const/volatile/restrict for pointers vs other types.
+ *
+ * For a good discussion of *PARSING* C syntax (as a human), see
+ * Peter van der Linden's "Expert C Programming: Deep C Secrets",
+ * Ch.3 "Unscrambling Declarations in C".
+ *
+ * It won't help with BTF to C conversion much, though, as it's an opposite
+ * problem. So we came up with this algorithm in reverse to van der Linden's
+ * parsing algorithm. It goes from structured BTF representation of type
+ * declaration to a valid compilable C syntax.
+ *
+ * For instance, consider this C typedef:
+ * typedef const int * const * arr[10] arr_t;
+ * It will be represented in BTF with this chain of BTF types:
+ * [typedef] -> [array] -> [ptr] -> [const] -> [ptr] -> [const] -> [int]
+ *
+ * Notice how [const] modifier always goes before type it modifies in BTF type
+ * graph, but in C syntax, const/volatile/restrict modifiers are written to
+ * the right of pointers, but to the left of other types. There are also other
+ * quirks, like function pointers, arrays of them, functions returning other
+ * functions, etc.
+ *
+ * We handle that by pushing all the types to a stack, until we hit "terminal"
+ * type (int/enum/struct/union/fwd). Then depending on the kind of a type on
+ * top of a stack, modifiers are handled differently. Array/function pointers
+ * have also wildly different syntax and how nesting of them are done. See
+ * code for authoritative definition.
+ *
+ * To avoid allocating new stack for each independent chain of BTF types, we
+ * share one bigger stack, with each chain working only on its own local view
+ * of a stack frame. Some care is required to "pop" stack frames after
+ * processing type declaration chain.
+ */
+int btf_dump__emit_type_decl(struct btf_dump *d, __u32 id,
+ const struct btf_dump_emit_type_decl_opts *opts)
+{
+ const char *fname;
+ int lvl, err;
+
+ if (!OPTS_VALID(opts, btf_dump_emit_type_decl_opts))
+ return -EINVAL;
+
+ err = btf_dump_resize(d);
+ if (err)
+ return -EINVAL;
+
+ fname = OPTS_GET(opts, field_name, "");
+ lvl = OPTS_GET(opts, indent_level, 0);
+ d->strip_mods = OPTS_GET(opts, strip_mods, false);
+ btf_dump_emit_type_decl(d, id, fname, lvl);
+ d->strip_mods = false;
+ return 0;
+}
+
+static void btf_dump_emit_type_decl(struct btf_dump *d, __u32 id,
+ const char *fname, int lvl)
+{
+ struct id_stack decl_stack;
+ const struct btf_type *t;
+ int err, stack_start;
+
+ stack_start = d->decl_stack_cnt;
+ for (;;) {
+ t = btf__type_by_id(d->btf, id);
+ if (d->strip_mods && btf_is_mod(t))
+ goto skip_mod;
+
+ err = btf_dump_push_decl_stack_id(d, id);
+ if (err < 0) {
+ /*
+ * if we don't have enough memory for entire type decl
+ * chain, restore stack, emit warning, and try to
+ * proceed nevertheless
+ */
+ pr_warn("not enough memory for decl stack:%d", err);
+ d->decl_stack_cnt = stack_start;
+ return;
+ }
+skip_mod:
+ /* VOID */
+ if (id == 0)
+ break;
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_PTR:
+ case BTF_KIND_VOLATILE:
+ case BTF_KIND_CONST:
+ case BTF_KIND_RESTRICT:
+ case BTF_KIND_FUNC_PROTO:
+ id = t->type;
+ break;
+ case BTF_KIND_ARRAY:
+ id = btf_array(t)->type;
+ break;
+ case BTF_KIND_INT:
+ case BTF_KIND_ENUM:
+ case BTF_KIND_FWD:
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ case BTF_KIND_TYPEDEF:
+ goto done;
+ default:
+ pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
+ btf_kind(t), id);
+ goto done;
+ }
+ }
+done:
+ /*
+ * We might be inside a chain of declarations (e.g., array of function
+ * pointers returning anonymous (so inlined) structs, having another
+ * array field). Each of those needs its own "stack frame" to handle
+ * emitting of declarations. Those stack frames are non-overlapping
+ * portions of shared btf_dump->decl_stack. To make it a bit nicer to
+ * handle this set of nested stacks, we create a view corresponding to
+ * our own "stack frame" and work with it as an independent stack.
+ * We'll need to clean up after emit_type_chain() returns, though.
+ */
+ decl_stack.ids = d->decl_stack + stack_start;
+ decl_stack.cnt = d->decl_stack_cnt - stack_start;
+ btf_dump_emit_type_chain(d, &decl_stack, fname, lvl);
+ /*
+ * emit_type_chain() guarantees that it will pop its entire decl_stack
+ * frame before returning. But it works with a read-only view into
+ * decl_stack, so it doesn't actually pop anything from the
+ * perspective of shared btf_dump->decl_stack, per se. We need to
+ * reset decl_stack state to how it was before us to avoid it growing
+ * all the time.
+ */
+ d->decl_stack_cnt = stack_start;
+}
+
+static void btf_dump_emit_mods(struct btf_dump *d, struct id_stack *decl_stack)
+{
+ const struct btf_type *t;
+ __u32 id;
+
+ while (decl_stack->cnt) {
+ id = decl_stack->ids[decl_stack->cnt - 1];
+ t = btf__type_by_id(d->btf, id);
+
+ switch (btf_kind(t)) {
+ case BTF_KIND_VOLATILE:
+ btf_dump_printf(d, "volatile ");
+ break;
+ case BTF_KIND_CONST:
+ btf_dump_printf(d, "const ");
+ break;
+ case BTF_KIND_RESTRICT:
+ btf_dump_printf(d, "restrict ");
+ break;
+ default:
+ return;
+ }
+ decl_stack->cnt--;
+ }
+}
+
+static void btf_dump_drop_mods(struct btf_dump *d, struct id_stack *decl_stack)
+{
+ const struct btf_type *t;
+ __u32 id;
+
+ while (decl_stack->cnt) {
+ id = decl_stack->ids[decl_stack->cnt - 1];
+ t = btf__type_by_id(d->btf, id);
+ if (!btf_is_mod(t))
+ return;
+ decl_stack->cnt--;
+ }
+}
+
+static void btf_dump_emit_name(const struct btf_dump *d,
+ const char *name, bool last_was_ptr)
+{
+ bool separate = name[0] && !last_was_ptr;
+
+ btf_dump_printf(d, "%s%s", separate ? " " : "", name);
+}
+
+static void btf_dump_emit_type_chain(struct btf_dump *d,
+ struct id_stack *decls,
+ const char *fname, int lvl)
+{
+ /*
+ * last_was_ptr is used to determine if we need to separate pointer
+ * asterisk (*) from previous part of type signature with space, so
+ * that we get `int ***`, instead of `int * * *`. We default to true
+ * for cases where we have single pointer in a chain. E.g., in ptr ->
+ * func_proto case. func_proto will start a new emit_type_chain call
+ * with just ptr, which should be emitted as (*) or (*<fname>), so we
+ * don't want to prepend space for that last pointer.
+ */
+ bool last_was_ptr = true;
+ const struct btf_type *t;
+ const char *name;
+ __u16 kind;
+ __u32 id;
+
+ while (decls->cnt) {
+ id = decls->ids[--decls->cnt];
+ if (id == 0) {
+ /* VOID is a special snowflake */
+ btf_dump_emit_mods(d, decls);
+ btf_dump_printf(d, "void");
+ last_was_ptr = false;
+ continue;
+ }
+
+ t = btf__type_by_id(d->btf, id);
+ kind = btf_kind(t);
+
+ switch (kind) {
+ case BTF_KIND_INT:
+ btf_dump_emit_mods(d, decls);
+ name = btf_name_of(d, t->name_off);
+ btf_dump_printf(d, "%s", name);
+ break;
+ case BTF_KIND_STRUCT:
+ case BTF_KIND_UNION:
+ btf_dump_emit_mods(d, decls);
+ /* inline anonymous struct/union */
+ if (t->name_off == 0)
+ btf_dump_emit_struct_def(d, id, t, lvl);
+ else
+ btf_dump_emit_struct_fwd(d, id, t);
+ break;
+ case BTF_KIND_ENUM:
+ btf_dump_emit_mods(d, decls);
+ /* inline anonymous enum */
+ if (t->name_off == 0)
+ btf_dump_emit_enum_def(d, id, t, lvl);
+ else
+ btf_dump_emit_enum_fwd(d, id, t);
+ break;
+ case BTF_KIND_FWD:
+ btf_dump_emit_mods(d, decls);
+ btf_dump_emit_fwd_def(d, id, t);
+ break;
+ case BTF_KIND_TYPEDEF:
+ btf_dump_emit_mods(d, decls);
+ btf_dump_printf(d, "%s", btf_dump_ident_name(d, id));
+ break;
+ case BTF_KIND_PTR:
+ btf_dump_printf(d, "%s", last_was_ptr ? "*" : " *");
+ break;
+ case BTF_KIND_VOLATILE:
+ btf_dump_printf(d, " volatile");
+ break;
+ case BTF_KIND_CONST:
+ btf_dump_printf(d, " const");
+ break;
+ case BTF_KIND_RESTRICT:
+ btf_dump_printf(d, " restrict");
+ break;
+ case BTF_KIND_ARRAY: {
+ const struct btf_array *a = btf_array(t);
+ const struct btf_type *next_t;
+ __u32 next_id;
+ bool multidim;
+ /*
+ * GCC has a bug
+ * (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=8354)
+ * which causes it to emit extra const/volatile
+ * modifiers for an array, if array's element type has
+ * const/volatile modifiers. Clang doesn't do that.
+ * In general, it doesn't seem very meaningful to have
+ * a const/volatile modifier for array, so we are
+ * going to silently skip them here.
+ */
+ btf_dump_drop_mods(d, decls);
+
+ if (decls->cnt == 0) {
+ btf_dump_emit_name(d, fname, last_was_ptr);
+ btf_dump_printf(d, "[%u]", a->nelems);
+ return;
+ }
+
+ next_id = decls->ids[decls->cnt - 1];
+ next_t = btf__type_by_id(d->btf, next_id);
+ multidim = btf_is_array(next_t);
+ /* we need space if we have named non-pointer */
+ if (fname[0] && !last_was_ptr)
+ btf_dump_printf(d, " ");
+ /* no parentheses for multi-dimensional array */
+ if (!multidim)
+ btf_dump_printf(d, "(");
+ btf_dump_emit_type_chain(d, decls, fname, lvl);
+ if (!multidim)
+ btf_dump_printf(d, ")");
+ btf_dump_printf(d, "[%u]", a->nelems);
+ return;
+ }
+ case BTF_KIND_FUNC_PROTO: {
+ const struct btf_param *p = btf_params(t);
+ __u16 vlen = btf_vlen(t);
+ int i;
+
+ /*
+ * GCC emits extra volatile qualifier for
+ * __attribute__((noreturn)) function pointers. Clang
+ * doesn't do it. It's a GCC quirk for backwards
+ * compatibility with code written for GCC <2.5. So,
+ * similarly to extra qualifiers for array, just drop
+ * them, instead of handling them.
+ */
+ btf_dump_drop_mods(d, decls);
+ if (decls->cnt) {
+ btf_dump_printf(d, " (");
+ btf_dump_emit_type_chain(d, decls, fname, lvl);
+ btf_dump_printf(d, ")");
+ } else {
+ btf_dump_emit_name(d, fname, last_was_ptr);
+ }
+ btf_dump_printf(d, "(");
+ /*
+ * Clang for BPF target generates func_proto with no
+ * args as a func_proto with a single void arg (e.g.,
+ * `int (*f)(void)` vs just `int (*f)()`). We are
+ * going to pretend there are no args for such case.
+ */
+ if (vlen == 1 && p->type == 0) {
+ btf_dump_printf(d, ")");
+ return;
+ }
+
+ for (i = 0; i < vlen; i++, p++) {
+ if (i > 0)
+ btf_dump_printf(d, ", ");
+
+ /* last arg of type void is vararg */
+ if (i == vlen - 1 && p->type == 0) {
+ btf_dump_printf(d, "...");
+ break;
+ }
+
+ name = btf_name_of(d, p->name_off);
+ btf_dump_emit_type_decl(d, p->type, name, lvl);
+ }
+
+ btf_dump_printf(d, ")");
+ return;
+ }
+ default:
+ pr_warn("unexpected type in decl chain, kind:%u, id:[%u]\n",
+ kind, id);
+ return;
+ }
+
+ last_was_ptr = kind == BTF_KIND_PTR;
+ }
+
+ btf_dump_emit_name(d, fname, last_was_ptr);
+}
+
+/* return number of duplicates (occurrences) of a given name */
+static size_t btf_dump_name_dups(struct btf_dump *d, struct hashmap *name_map,
+ const char *orig_name)
+{
+ char *old_name, *new_name;
+ size_t dup_cnt = 0;
+ int err;
+
+ new_name = strdup(orig_name);
+ if (!new_name)
+ return 1;
+
+ hashmap__find(name_map, orig_name, (void **)&dup_cnt);
+ dup_cnt++;
+
+ err = hashmap__set(name_map, new_name, (void *)dup_cnt,
+ (const void **)&old_name, NULL);
+ if (err)
+ free(new_name);
+
+ free(old_name);
+
+ return dup_cnt;
+}
+
+static const char *btf_dump_resolve_name(struct btf_dump *d, __u32 id,
+ struct hashmap *name_map)
+{
+ struct btf_dump_type_aux_state *s = &d->type_states[id];
+ const struct btf_type *t = btf__type_by_id(d->btf, id);
+ const char *orig_name = btf_name_of(d, t->name_off);
+ const char **cached_name = &d->cached_names[id];
+ size_t dup_cnt;
+
+ if (t->name_off == 0)
+ return "";
+
+ if (s->name_resolved)
+ return *cached_name ? *cached_name : orig_name;
+
+ if (btf_is_fwd(t) || (btf_is_enum(t) && btf_vlen(t) == 0)) {
+ s->name_resolved = 1;
+ return orig_name;
+ }
+
+ dup_cnt = btf_dump_name_dups(d, name_map, orig_name);
+ if (dup_cnt > 1) {
+ const size_t max_len = 256;
+ char new_name[max_len];
+
+ snprintf(new_name, max_len, "%s___%zu", orig_name, dup_cnt);
+ *cached_name = strdup(new_name);
+ }
+
+ s->name_resolved = 1;
+ return *cached_name ? *cached_name : orig_name;
+}
+
+static const char *btf_dump_type_name(struct btf_dump *d, __u32 id)
+{
+ return btf_dump_resolve_name(d, id, d->type_names);
+}
+
+static const char *btf_dump_ident_name(struct btf_dump *d, __u32 id)
+{
+ return btf_dump_resolve_name(d, id, d->ident_names);
+}